Mandrels for making seamless bends in rectangular tubing



April 21, 1959 F. J. FUCHS, JR, ET AL 2,882,951 MANDRELS FOR MAKING SEAMLESS BENDS IN RECTANGULAR TUBIIIIIGI Filed Feb. 26. 1954 4 Sheets-Sheet 1 INVENTORS. FRANCIS J. FUCHS ,JR., 6 BY GEORGE NEVRINCEAN as kml YATTOIYTNEY April 21, 1959 I F. J. FUCHS, JR, ET AL MANDRELS FOR MAKING SEAMLESS BENDS IN RECTANGULAR TUBING Filed Feb. 26, 1954 4 She cs-Sheet 2 INVENTORS FRANCIS J. FUCHS,JR.,& GEORGE NEVRINCEAN ATTORNEY April 21, 1959 F. J. FUCHS, JR., ETAL 2,382,951

MANDRELS FOR MAKING SEAMLESS BENDS IN RECTANGULAR TUBING Filed Feb. 26, '1954 4 Sheets-Sheet 3 INVENTORS FRANCIS J. FUQHS, JR., a By GEORGE NEVRINCEAN.

lmqwiy ATTORNEY April 21, 1959 F. J. FUCHS, JR., 'ET AL 2,882,951

55 BENDS IN RECTANGULAR TUBING I MANDRELS FOR MAKING SEAMLE Filed Feb. 26, 1954 4 Sheets-Shet' 4 I INVENTORS. FRANCIS J.FUCHS,JR., a GEORGE NEVRINCEAN og kfiuw ATTORNEY.

MANDRELS FOR MAKING SEAMLESS BEN DS IN RECTANGULAR TUBING Francis J. Fuchs, In, Winston-Salem, N.C., and George Nevrincean, Florham Park, NJ., assignors to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Application February 26, 1954, Serial No. 412,708

4 Claims. (Cl. 153-4 This invention relates to apparatus for making bends in tubing, and more particularly to mandrels for sup porting the interior of rectangular tubing while effecting seamless bends therein.

In the fabrication of rectangular, thin-walled metallic wave guide tubing it frequently becomes necessary to effect in the tubing sharp bends of predetermined angles. It is also necessary that the interior dimensions of the tubing be maintained substantially constant in order to prevent alteration of the electrical transmission characteristics of the tubing. Prior to this invention it has been difiicult or impossible to effect a seamless bend in such tubing and still maintain the necessary uniform internal dimensions.

In accordance with the disclosure of a co-pending application of Francis J. Fuchs, Jr., Serial No. 412,730, filed February 26, 1954, relating to apparatus for making seamless bends in rectangular tubing, a straight length of rectangular wave guide tubing is subjected to a bending operation wherein one wall of the tube is bent in the form of a sharp angle and a second, parallel wall of the tube is made to assume the shape of a smooth curve having a radius of curvature equal to the width of the tube.

The present invention relates specifically to a mandrel for supporting the interior of a rectangular tube subjected to the bending operation as disclosed in the aforesaid co-pending application.

Accordingly it is an object of the present invention to provide a mandrel for supporting the interior of a rectangular tube when said tube is subjected to a first sharp angular bend.

It is a further object of this invention to provide a mandrel for supporting the interior of a rectangular tube when said tube is subjected to a second sharp angular bend.

It is a still further object of this invention to provide a mandrel for maintaining substantially uniform the interior of a rectangular tube during the bending thereof.

In accordance with the above objects, in a first embodiment of the invention, there is provided a mandrel comprising a stem adapted for connection at one extremity thereof to a movable mandrel shaft and adapted for slidable insertion into a rearward portion of a tube to be bent, said stem having apertured flanges at the other extremity thereof for rotatable interleaving engagement with an apertured, flanged pivot block. A body member is slidably insertable into a forward portion of the tube and detachably secured to the pivot block. The peripheries of the flanges of the stem and of the pivot block are provided with convex arcuate surfaces which, when the pivot block and attached body member are rotated through a predetermined angle relative to the stern, form a sub- States Patent 2,882,951 Patented Apr. 21., 1959 "ice stantially continuous surface corresponding in shape to the final bent configuration of one wall of the tube. The stem and the body member are provided with adjacent plane surfaces which, upon rotation of the pivot block and the attached body member relative to the stem member, form a substantially continuous angular surface for supporting a second wall of the tube to be bent.

A second embodiment of the present invention comprises a mandrel for supporting, during a second bending operation, the interior of a tube having a first bend therein as effected by the first embodiment. In this embodiment there is provided a stem similar to that of the first embodiment, a laminated pivot block consisting of top, intermediate and bottom plates, and a body slidably insertable into the bent portion of the tube and comprising a connecting block for attaching the body to the pivot block and for providing a supporting surface for a wall of the tube to be angularly bent, an end member, and curvilinear top and bottom links for attaching the connecting block to the end member and for allowing insert ion of the body around the first bend in the tube.

Other objects and advantages will become apparent from an examination of the following description when taken in conjunction with the accompanying drawings, wherein:

Fig. l is a top plan view, partly in cross section, of the first embodied mandrel in initial position within a tube before bendng;

Fig. 2 is a view similar to Fig. 1 after the first bending operation;

Fig. 3 is a perspective view of the tube after the first bending operation;

Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 5 is a bottom plan view of a portion of the first embodied mandrel;

Fig. 6 is a cross-sectional view taken on line 6-6 of Fig. 5;

Fig. 7 is an exploded perspective view illustrating the first embodiment of the invention, with the parts reversed end for endfrom their positions shown in Figs. 1, 4 and 5;

Fig. 8 is a top plan view, partly in cross section, of the second embodiment in position inside a tube prior to the second bending operation;

Fig. 9 is a view similar to Fig. 8 after the second bending operation; 7

Fig. 10 is a perspective view of the tube after the completion of the second bending operation;

Fig. 11 is a cross-sectional plan view showing the inandrel in the position of Fig. 9;

Fig. 12 is a perspective view of the second embodiment of the invention showing the body portion of the mandrel disconnected from the stem and the pivot block;

Fig. 13 is a perspective view of the connecting block of the body of the second embodiment; i

Fig. 14 is a perspective view of the upper plate of the pivot block of the second embodiment;

Fig. 15 is a perspective view of the bottom plate of the pivot block of the second embodiment;

Fig. 16 is a perspective view of the intermediate plate of the pivot block of the second embodiment; and

Fig. 17 is a perspective view of the bottom link of the body of the second embodiment.

Reterring nowto the drawings wherein like reference numerals designate the same parts throughout the several views, and in particular 'to- Figs. -4 and- 7, the numeral 1 4 designates generally a stem consisting of an upper stem member 15' adapted at one extremity thereof for connection to a reciprocable mandrel shaft 16 for slidable insertion into a rearward portion of a tube 12 to be bent. The upper stem member 15 is further provided near said one extremity thereof with a peripherally extending first abutment 13 for abutting a rearward extremity of the tube to be bent. The other or free extremity of the upper stem member 15 is provided with an upper stem flange 17 having an aperture 18 therein and having a portion of the periphery thereof formed in the shape of a convex arcuate surface 19 having a radius of curvature substantially equal to the width of the upper stem member 15. The upper stem member 15 is also provided with concave arcuate shoulders 20 and 22 adjacent the flange 17. The lower surface of the upper stem member 15, near the free extremity thereof, is cut out as at 23.

A lower stem member 24 is secured by suitable means such as one or more dowel pins 25 in apertures 35 and screws 26 in apertures 27 to the cut out portion 23 of the upper stem portion 15. The lower stem member 24 is provided at one extremity thereof with a lower stemflange 28 having a configuration the same as flange 17 and having a corresponding aperture 29 and a convex arcuate surface 31. The lower stem member 24 is also provided with a concave arcuate shoulder 30 identical to the shoulders 20 and 22 of the upper stem member. Arcuate shoulders 20, 22 and 30 are provided for portions of their lengths with plane surfaces 32, 33 and 34, respectively.

The numeral 36 designates generally a pivot block having a rectangular portion 37 which is provided at one extremity thereof with a threaded aperture 38. Projecting from the other extremity of the rectangular portion 37 are three parallel, spaced pivot block flanges or plates 39. Each of the pivot block flanges 39 is provided with a convex arcuate surface 40 similar to the convex arcuate surfaces 19 and 31 on the stem flanges 17 and 28, respectively. Each of the flanges 39 is further provided with an aperture 42 and an angular notch 43. The rectangular portion 37 of the pivot block is provided with concave arcuate shoulders 45 adjacent the pivot block flanges 39 (Fig. w The stem flanges 17 and 28 are positioned between the pivot block flanges 39 and are held in rotatable engage ment therewith by means of a pivot pin 41 in which position the peripheries of the pivot block flanges 39 are in slidable engagement with the concave arcuate shoulders 20, 22 and 30, the stem flanges 17 and 28 are in slidable engagement with the concave arcuate shoulders 45, and the convex arcuate surfaces 19 and 31 on the upper stem member and the lower stem member, respectively, are displaced from the corresponding surfaces 40 on the pivot block flanges 39 by a predetermined angle, for example, 45 degrees.

The numeral 44 designates a body member which is slidably insertable into a forward portion of the tube to be bent, and is provided near one extremity thereof with a peripherally extending second abutment 46 for engagement with a forward extremity of the tube. The body member 44 is provided at the other extremity thereof with bifurcations 47 and 48which define a rectangular cavity 49 for engagement with the rectangular portion 37 of the pivot block. The body member 44 is provided with a longitudinally extending passage 50 which is alignable with the threaded aperture 38 in the rectangular portion 37 of the pivot block, said passage being reduced in cross section for a portion of its length for abutting engagement with the enlarged head of connecting member 52 by means of which the body member 44 is detachably secured to the pivot block 36. The extremities of the bifurcations 47 and 48 are provided with curved surfaces 53 and 54, respectively, for engagement with the pivot block flanges 39 and the stem flanges 17 and 28. The body 44 provided with a slot 56 extending across the width of the bifurcation 48. A flat rectangular panel 57 is secured in the slot 56 by suitable means, such as screws through apertures 59. One extremity of the panel 57 extends beyond the extremity of the bifurcation 48 into engagement with the angular notches 43 in the pivot block flanges 39. The projecting portion of the panel 57 is provided with arcuate grooves 58 to allow relative movement between the body member 44 and the stem flanges 17 and 28.

The operation of this embodiment of the invention is hereinbelow described.

The tube 12 to be bent is placed in position in a suitable bending apparatus (Fig. 1) which may comprise a wiper die 60, a forming die 62, a pressure die 63 and a clamping die 64. Such bending apparatus may be generally of the type disclosed in the aforementioned copending application. The stem 14 with the attached pivot block 36 is connected to the reciprocable mandrel shaft 16 and the attached stem and pivot block are inserted into the rearward portion of the tube 12 until the abutment 13 contacts the rearward extremity of the tube. The body member 44 with the attached panel 57 is then manually inserted into the forward portion of the tube 12 until the abutment 46 engages the forward extremity of the tube and the connecting member 52 is threadedly engaged with the aperture 38 in the pivot block 36. The bending apparatus is then actuated through the desired angle of bend (Fig. 2), for example, degrees. The convex arcuate surfaces 40 on the pivot block flanges 39 are thereby rotated into alignment with the corresponding surfaces 19 and 31 on the stem flanges 17 and 28, respectively, thereby forming a substantially continuous curvilinear surface having a radius of curvature substantially equal to the width of the mandrel and hence also substantially equal to the interior width of the tube to be bent. This continuous curvilinear surface thereby serves to support a first wall 66 of the tube 12 in the desired shape of a smooth curve 61 (Fig. 3) having a radius of curvature substantially equal to the width of the tube.

The panel 57, the body member 44 and the stem members 15 and 24 provide plane surfaces for supporting a second wall 67 of the tube 12 during the bending thereof. A sharp angle as at 68 is formed in the wall 67 at a point opposite the center of rotation of the pivot block 36 and at approximately the center of radius of the curve 61. When the tube and associated mandrel body 44 have been rotated through a predetermined desired angle the panel 57 contacts the plane surfaces 32, 33 and 34 on the shoulders 20, 22 and 30, respectively, thereby producingthe sharp corner 68 of the desired degree of angularity.

The abutments 13 and 46 on the stem member 15 and the body member 44, respectively, tightly grip the extremities of the tube 12 during the bending operation for the purpose of restraining any undesired movement of the tube. This restraining action upon the tube has the further eifect of slightly compressing the tube between the point of bend and the forward extremity thereof, thereby preventing an undesirable thinning of the wall 66 in the bent portion thereof.

At the completion of the bending operation the con necting member 52 is loosened and the body member 44 is removed from the bent tubing whereupon the stem 14 and the attached pivot block 36 may be retracted by the mandrel shaft 16 from the rearward portion of the tube.

The tube 12 is shown in Fig. 3 at the completion of the above described first bending operation.

A second embodiment of the present invention is disclosed in Figs. 8 through 16. Fig. 12 shows a stem 14 consisting of an upper stem member 15 and a lower stem member 24 secured together by dowel pins 25 in apertures 35 and screws 26 in apertures 27 similar to the correspondingly numbered parts of the first embodiment of the mandrel. As in the first embodiment the stem 14 is adapted for connection at one extremity thereof to a reciprocable mandrel shaft 16 (not shown) and is slidably insertable into a rearward portion of a tube 12 to be bent (Fig. 8). Similarly, the stem 14 is provided with a peripherally extending first abutment 13 for con tacting a rearward extremity of the tube. The upper stem member 15 and the lower stem member 24 are provided with stem flanges 17 and 28 as in the first embodiment of the invention as disclosed in Fig. 7. As in the first embodiment, the flanges 17 and 28 are provided with apertures 18 and 29, respectively, and with convex arcuate surfaces 19 and 31, respectively.

The numeral 69 designates generally a pivot block consisting of an upper plate designated generally in Fig. 14 by the numeral 70, a. lower plate 72 (Fig. 15), and an intermediate plate 73 (Fig. 16). Plates 70 and 72 are identical in configuration, being provided with generally semicircular flange portions '74 and 76, respectively, and being also provided with first angular notches '77 and 78, respectively, and with second angular notches 79 and 80, respectively. The plates 70 and 72 are further provided with apertures 82 and 83, respectively, and with openings 84 and 86, respectively. The peripheries of the plates 70 and 72 are provided with convex arcuate surfaces 87 and 88, respectively, said surfaces 87 and 88 corresponding in shape to the arcuate surfaces 19 and 31 on the stem flanges 17 and 28, respectively, and each having a radius of curvature substantially equal to the width of the stem 14.

The intermediate plate 73 is provided with a projecting member or flange 89 provided with an aperture 99 and having a convex arcuate surface 92 corresponding to the surfaces 87 and 88 on the flange portions 74 and 76 of the plates 70 and 72.. The intermediate plate 73 is also provided with concave arcuate shoulders 93 and 94 adjacent the flange 89, and with a first angular notch 96, a second angular notch 91, an aperture 97 and a threaded passage 99 (Fig. 11) interconnecting with the first angular notch 96.

The plates 70, 72 and 73 are held in fixed, aligned relationship by means of a pin 100 extending through the openings 84, 86, and 97. The flange portions 74 and 76 of the plates 70 and 72 and the flange 89 of the plate 73 are held in rotatable, interleaving relationship with the stem flanges 17 and 28 by means of a pivot pin 102 extending through the apertures 82, 18, 90, 29 and 83 in the respective flanges. In this position the pivot block flanges 74, 89 and 76 are in slidable engagement with the concave arcuate shoulders 20, 22 and 30, re spectively, on the stem 14 (Fig. 7), and the stem flanges 17 and 28 are in slidable engagement with the concave arcuate shoulders 93 and 94, respectively, of the plate 73. Similar to the disclosure of the first embodiment of the present invention, when pivot block flanges 7'4, 89 and 76 are in an unrotated position, the convex arcuate surfaces 87, 92 and 88 are displaced from the corresponding surfaces 19 and 31 on the stem flanges by a predetermined angle, for example, 45 degrees.

The numeral 103 (Fig. 12) designates generally a bod}. member adapted for insertion into a forward portion of a tube 12 which has been subjected to a prior bending operation in accordance with the preceding disclosure of the first embodiment of the present invention.

In Fig. 13, the numeral 104 designates a connecting block having a flange 106 which is provided upon its upper and lower surfaces with cylindrical bosses 107. Connecting block 104 is also provided with concave arcuate shoulders 108 adjacent the flange 106 and with an angular projection 109 having a shape complementary to the angular notches 77, 96 and 78 in the plates 70, 73, and, 72. The connecting block 104 is further provided with a passage 110 extending through the flange 106 and terminating in surfaces comprising and adjacent the angular projection 109 so as to be alignable with the passage 99 in the intermediate plate 73. A set screw 112 (Fig. 11) is threadedly engageable with a threaded passage 113 which interconnects with the passage 110 in the connecting block 104.

The connecting block 104 is also provided with a slot 114 for the reception therein of a flat, rectangular panel 116 which, when secured to the connecting block 104 by suitable means such as dowel pins or telescopic screws 117 in apertures 118, projects beyond one extremity of the connecting block 104. In the assembled position of the mandrel the projecting portion of the panel 116 engages the angular notches 79, and 91 in the plates 70, 72 and 73. The projecting portion of the panel 116 is provided with arcuate grooves 119 to accommodate the stem flanges 17 and 28 and to allow relative movement between the said stern flanges and the body 103. The panel 116 is similar to the panel 57 of Fig. 7.

An upper link 120 and a similar complementary lower link 122 (Fig. 17) are pivotally connected at corresponding first extremities thereof to the connecting member 104 by means of first link flanges 123 having therein apertures 124 adapted to rotatably engage the bosses 107 on the connecting flange 106. In this position the first link flanges 123 are slidably engageable with the concave arcuate shoulders 108 on the connecting block 104. The links 120 and 122 are provided with concave arcuate shoulders 126 adjacent the first link flanges 123 and in the assembled position of the links and the connecting block, the shoulders 126 are in slidable engagement with the connecting flange 106.

The links 120 and 122 are provided at second corresponding extremities thereof with second link flanges 127 having apertures 128 and convex arcuate surfaces 129. The links 120 and 122 are also provided with concave arcuate shoulders 130 adjacent the second link flanges 127. The links 120 and 122 are further provided with concave, curvilinear surfaces 132 and with passages 133 which, in the assembled position of the links, define a circular aperture alignable with the passage in the connecting block 104.

The numeral 134 designates an end member which is pivotallyengageable with the links and 122 by means of a projecting member or end flange 136 extending from one extremity of the end member and having protuberances or bosses. 137 formed on the upper and lower surfaces thereof. The end member 134 is also provided with concave arcuate shoulders 138 adjacent the end flange 136 and with a convex arcuate surface 139, on the end flange 136, similar to the surfaces 129 on the second link flanges 127. The bosses 137 are insertable into the apertures 12 8 of the second link flanges 127 in which position the end flange 136 is in slidable engagement with the concave arcuate shoulders on the links 120 and 122, and the second link flanges 127 are in slidable engagement with the concave arcuate shoulders 138 on the end member 134. When the end member and the links are in a straight line relationship (Fig. 12) the convex arcuate surface 139 on the end flange 136 is displaced from the corresponding surfaces 129 on the second link flanges 127 by a predetermined angle, for example, 45 degrees. This displacement occurs'because the arcuate surfaces 129 and 139 are located on the second link flanges 127 and end flange 136 in such a position that said arcuate surfaces will cooperate to form a continuous, convex-arcuate surface (139 in Fig. 11) when the man drel sections have been rotated through said predetermined angle. The end member 134 is provided with a passage 140 similar to the passage 133 in the links 120 and 122, and with a second peripherally extending abutment 142 for engaging a forward extremity of the tube 12 to be bent. An aperture 141 is provided in the end member 134 to aid in the removal of the body 103 from the tube 12.

The operation of the second embodiment of the invention is described below.

The tube 12, which previously has been bent in accordance with the preceding disclosure of the first embodiment, is positioned in a suitable bending apparatus, comprising, for example, the previously described wiper die 60, forming die 62, pressure die 63 and clamping die 64 (Fig. 8). The assembled stem 14 and pivot block 69 are connected to the reciprocable mandrel 16 and inserted into the rearward portion of the tube 12 until the first abutment 13 contacts the rearward extremity of the tube 12. The body member 103, consisting of the assembled connecting block 104, upper and lower links 120 and 122 and end member 134, is then manually inserted into the forward portion of the bent tube. The curvilinear surfaces 132 and the pivotable nature of the links 120 and 122 about the bosses 137 allow the body 103 to be inserted around the sharp corner 68 and to assume an angular configuration corresponding to that of the tube, thereby bringing into mutual alignment the convex arcuate surfaces 129 on the second link flanges 127 and the similar surface 139 on the end flange 136. The surfaces 129 and 136 thereby present a substantially continuous surface having a radius of curvature substantially equal to the radius of the bent portion 61 of the wall 66 of the tube 12. In this position the passages 99, 110, 133 and 140 in the intermediate member 73, the connecting block 104, the links 120 and 122, and the end member 134, respectively, are aligned to define a continuous straight passage. A threaded connecting member 143, mounted in the passage 110 in the connecting block 104, is then engaged with the threaded passage 99 in the intermediate plate 73 to secure the body 103 to the pivot block 69, thereby drawing the second abutment 142 on the end member 134 into tight engagement with the forward extremity of the tube 12.

The bending apparatus is then actuated through a predetermined angle, for example, 45 degrees (Fig. 9), whereupon a second sharp corner 144 is formed in the wall 67 of the tube 12 and a second smooth curve 146 is formed in the wall 66 of the tube 12.

At the completion of this second bending operation the connecting member 143 may be loosened and the body 103 removed from the forward portion of the tube whereupon the stem 14 and associated pivot block 69 may be retracted from the rearward portion of the tube by the mandrel shaft 16 and the tube then removed from the bending apparatus. The set screw 112 engages the threaded connecting member 143 to hold the member 143 in the passage 110 in the connecting block 104 when the body 103 is disconnected from the pivot block 69.

The tube 12 is shown in Fig. at the completion of the above described second bending operation.

It will be understood that the above described embodiments are merely illustrative of the present invention and that other modifications could be made by those skilled in the art without departing from the spirit and scope of the present invention.

What is claimed is:

1. A mandrel for bending rectangular tubing, which comprises a stem slidably insertable into one extremity of a tube to be bent and having a plurality of spaced apertured flanges on one extremity thereof, said stem being provided with a plurality of concave arcuate shoulders adjacent to said flanges, a block having a plurality of substantially circular apertured plates on one extremity thereof and provided with an arcuate surface corresponding to a desired configuration of one wall of the tubing to be bent, means positioned in the apertures in said flanges and plates to pivotally connect said flanges and plates in interleaved relation thereby holding said plates in slideable engagement with said concave arcuate shoulders, a body having a bore therethrough and being slidably insertable into another extremity of the tubing, said bore being accessible externally of the tubing after said body is inserted into said tubing, means projecting through said bore to connect said body detachably to said block, said block being sufliciently short in relation to the internal dimensions of the tubing to permit removal thereof from the tubing after completion of a bending operation, and means associated with said body which abut said concave arcuate shoulders when said body and said block are pivoted through a predetermined angle relative to said stern so that said body and said stem form adjacent planar surfaces disposed at an angle to each other for supporting the opposite wall of said tubing in the form of a sharp angle.

2. A mandrel for producing a single sharp bend in a rectangular tube having a first sharp bend therein, which comprises a stem having a plurality of apertured, arcuate flanges extending from one extremity thereof and being slidably insertable into a straight portion of the tube to be bent, a block having a plurality of apertured arcuate plates which extend from one extremity thereof, and are provided with angular notches, means positioned in the apertures of said flanges and plates to pivotally connect said flanges and plates in interleaved relation, and a flexible body slidably insertable into an angularly bent portion of said tube, said body having a bore extending therethrough, means projecting through said bore to detachably secure said body to said block such that a portion of said block engages said notches of said plates, whereby when said body and said block are pivoted relative to said stem, the body and stem provide adjacent planar surfaces disposed at an angle to each other for supporting one wall of said tube in the form of a sharp angle and said arcuate flanges and arcuate plates provide a substantially continuous surface for supporting another wall of said tube in the form of a smooth curve.

3. A mandrel for effecting angular bends in rectangular tubes, which comprises a stem having a plurality of apertured flanges extending from one extremity thereof, portions of the peripheries of said flanges being contoured in the form of arcs having radii of curvature substantially equal to the width of a tube to be bent, a block having a plurality of apertured angularly notched plates extending from one extremity thereof, said plates having arcuate surfaces thereon similar to the arcuate portions of said flanges, means positioned in the apertures of said flanges and plates to pivotally connect the flanges and plates in interleaved relation whereby said arcuate surfaces of said plates are angularly displaced from arcuate portions of said flanges, and a body having a bore extending therethrough, means projecting through the bore to secure detachably said body to said block such that a portion of said body engages the angular notches of said plates, whereby when said body and said block are pivoted relative to said stem the body and stem provide two planar surfaces disposed at an angle to each other for supporting one wall of the tube in the form of a sharp angle and said arcuate surfaces of said plates are aligned with said arcuate portions of said flanges to provide a substantially continuous curved surface for supporting the opposite wall of the tube in the form of a smooth curve.

4. A mandrel for producing a second angular bend in a rectangular tube having a first sharp bend therein, which comprises a rigid stem slidably insertable into a straight portion of a tube to be bent, said stem being provided at one extremity thereof with a first peripherally extending abutment for engaging one extremity of said tube and provided at the other extremity with a plurality of arcuate apertured flanges, a block having a plurality of arcuate, apertured plates extending from one extremity thereof, means positioned in the apertures in said flanges and said plates to pivotally connect the flanges and plates in interleaved relation, a flexible body slidably insertable into an angular portion of said tube, said flexible body comprising a connecting block having raised bosses on l top and bottom surfaces thereof, a pair of links having first and second arcuate apertured extremities, said links being pivotally engageable, by means of said apertures at first extremities thereof, with said bosses, each of said links having a curvilinear surface thereon to enable said flexible body to be inserted around said first angular bend, an end member having near one extremity thereof a second peripherally extending abutment for engaging the other extremity of said tube, said end member being also provided with protuberances on top and bottom surfaces thereof for pivotal engagement by means of said second apertures with second extremities of said links, said flexible body having a bore extending through said connecting block, said links and said end member, and means projecting through said bore to detachably secure said flexible body to said block, whereby when said flexible body and said block are pivoted relative to said stem, the flexible body and stem provide adjacent planar surfaces disposed at an angle to each other for supporting one wall of said tube in the form of a sharp angle and said arcuate flanges and arcuate plates provide an arcuate surface for supporting another wall of said tube in the form of a smooth cuive.

References Cited in the file of this patent UNITED STATES PATENTS 1,075,045 Lewis Oct. 7, 1913 1,261,191 Vallone Apr. 2, 1918 1,308,591 James July 1, 1919 1,324,940 Theberath Dec. 16', 1919 1,370,074 Vasselli Mar. 1, 1921 1,683,572 Mueller Sept. 4, 1928 1,826,403 OBrien Oct. 6, 1931 2,057,359 Baker Oct. 13, 1936 2,528,315 Martin Oct. 31, 1950 FOREIGN PATENTS 5,019 Great Britain Apr. 23, 1885 18,986 Great Britain Sept. 3, 1903 

